Method for producing organofunctional siloxanes and use of same

ABSTRACT

Process for the preparation of organofunctional polysiloxanes, which comprises reacting cyclic dialkylsiloxanes with at least one compound of the type HO-R&#39;-X, wherein X=-OH, -COOH, -NR&#39;&#39;2-, -CR&#39;&#39;=CR&#39;&#39;2, and R=alkyl, aryl, alkylene, oxyalkylene or arylene, in the presence of an equilibration catalyst.

The present invention relates to a process for the production ofSi—O—C-linked organofunctional siloxanes and to the use thereof.

Organofunctionally modified siloxanes are widely used for modifyingorganic polymers. Siloxanes have hitherto been produced by means oftwo-stage production processes, in which the siloxane skeleton isinitially synthesised and the desired organofunctional group is thenintroduced in a second step.

DE-A 3 334 782 discloses the reaction of an acetoxy end-stoppedpolysiloxane with dihydroxy compounds with elimination of acetic acid,while U.S. Pat. No. 578 562 describes the reaction of an SiOHend-stopped polysiloxane with diols with elimination of water. U.S. Pat.No. 3,419,634, U.S. Pat. No. 3,821,325 and U.S. Pat. No. 3,832,419describe processes for reacting Si—Cl end-stopped siloxanes withdihydroxyaryl groups and the use thereof as intermediates for theproduction of organopolysiloxane/polycarbonate block polymers. Thistwo-stage process is, however, highly complex.

The object of the present invention was to provide a simplified processfor the production of organofunctional siloxanes.

It has now been found that organofunctional polysiloxanes may verystraightforwardly be produced by reacting cyclic dialkylsiloxanes withat least one compound of the type HO—R′—X, where X═—OH, —COOH, —NH₂—,—CH═CH₂ and R′ is alkylene or arylene, in the presence of anequilibration catalyst, optionally in a hydrophobic solvent.

The present invention accordingly provides a process for the productionof organofunctional polydiorganosiloxanes of the formula (I)

[R₂(XR′O)SiO_(½)]_(a)[R₂SiO_({fraction (2/2)})]_(b)[R₃SiO_(½)]_(2-a)

where

0<a≦2, preferably 2,

b=0-500, preferably 20-100, and with the proviso that where b=0, a is 2in the total,

X═—OH, —COOH, —NR″₂, —CR″═CR″₂,

R═C₁-C₁₈ alkyl, C₆-C₁₄ aryl, preferably phenyl, tolyl, C₂ and/or C₃alkyl, and R′═C₂-C₁₈ alkylene, oxyalkylene, such as for example2,2-bis-hydroxymethyl-l-butenol dialkyl ether, C₆-C₁₄ arylene and R″═Hand/or C₁-C₁₈ alkyl, wherein the [R₂SiO_({fraction (2/2)})] units areoptionally attached together via O—R′—O linkages,

characterised in that at least one cyclic dialkylsiloxane is reactedwith at least one compound of the type HO—R′—X in the presence of atleast one equilibration catalyst, optionally in the presence of lineartrialkylsiloxy-terminated siloxanes, preferably hexamethyldisiloxane,and optionally in a hydrophobic solvent

at temperatures of between 80 and 220° C., preferably of 130-170° C.

In another preferred embodiment of the process according to theinvention, 0.5≦a≦1.5 applies in the organofunctional polysiloxane of theformula (I), i.e. they contain trimethylsiloxy groups. In the case ofacid catalysis, the trimethylsiloxy groups are preferably added ashexamethyldisiloxane. In the case of alkaline catalysis, it is preferredto add short-chain trialkylsiloxy end-stopped siloxanes having C₁-C₁₈alkyl, preferably methyl.

Cyclic dialkylsiloxanes having 4, 5 or 6 silicon atoms, preferably 4 or5 silicon atoms, and bearing methyl residues as the alkyl residues arepreferably used in the process according to the invention.

In a preferred embodiment of the process according to the invention, thecyclic dialkylsiloxane used comprises a mixture of cyclicdialkylsiloxane with up to 50 wt. % of short-chain hydroxy-terminateddialkylpolysiloxanes of the formula[HO_(½)]₂[R₂SiO_({fraction (2/2)})]_(n) where n=2-50. This mixturepreferably comprises such a mixture as is obtained from the hydrolysisof chlorosilanes. In this case, water is formed by condensation of theSiOH group as well as the water from the reaction of the compound of thetype HO—R′—X with the mixture.

A hydrophobic solvent is preferably additionally used to facilitateremoval of the water of reaction.

An equilibration catalyst is taken to be a catalyst which is responsiblefor both chain synthesis and chain degradation in the reaction.

Equilibration catalysts preferably used in the process according to theinvention comprise perfluoroalkylsulfonic acids, preferably C₁-C₆perfluoroalkylsulfonic acids, individually or mixed with sulfuric acid,or alkali metal hydroxides, preferably potassium and caesium hydroxide.The equilibration catalyst is here preferably used in quantities of500-5000 ppm, relative to the quantities of cyclic dialkylsiloxane andthe compound HO—R′—X.

Selection of the catalyst is here determined by the functional alcoholused. In the case of aminoalcohols, basic catalysis is accordinglypreferred, while in the case of phenolic alcohols or hydroxycarboxylicacids, acidic catalysis is preferred.

In the case of certain compounds of the type HOR′X, acid catalysisbrings about not only the desired reaction, but also secondary reactionsinvolving ether and ester formation or cleavage of the compound HOR′X.Ether formation is a particular problem with diols, which may form 5- or6-membered cyclic ethers, such as for example the formation ofdimethyltetrahydrofuran from 2,5-hexanediol. Diol cleavage is inparticular observed in bishydroxyphenylalkanes, such as for example inthe reaction of 2,2-bis-(4-hydroxyphenyl)propane to yield phenol andisopropenylphenol. These reactions may be partially avoided by suitablecatalyst selection. Basic catalysts, such as for example caesiumhydroxide, are preferred in this case. The cyclic dialkylsiloxane ispreferably used in a ratio of 1 to 500 mol of dialkylsiloxy groups to 2mol of the compound of the type HO—R′—X.

The hydrophobic solvent used in the process according to the inventionpreferably has a boiling point of ≧100° C. at atmospheric pressureand/or forms an azeotropic mixture with water. A certain degree ofsolubility of the compound of the type HOR′X used in the solvent usedand/or in the siloxane, is favourable for the performance of the processaccording to the invention. Xylene, toluene or chlorobenzene arepreferably used.

By using a hydrophobic solvent which has a boiling point of above 100°C. and/or a solvent which forms a minimum azeotropic mixture with water,it is possible to remove the water by refluxing in conventional waterseparators, while simultaneously controlling the rate of reaction. Ithas proved advantageous if the compound of the type HOR′X used has aboiling point above the solvent used and does not form an azeotropicmixture with water. Preferred combinations in this case are:toluene/hydroquinone, xylene/hydroquinone,xylene/2,2-bis(hydroxymethyl-1-butenol) diallyl ether as well asxylene/2,2-bis-(4-hydroxycyclohexyl)propane.

If compounds of the type HO—R′—X in which X═OH, i.e. dihydroxycompounds, are used in the process according to the invention,O—Si(R₂)—O—R′—O—Si(R₂)—O— linkages are also formed. The minimum ratio ofSi(R₂)—OR′—OSiR₂ groups to the desired Si(R₂)—OR′OH end groups isprimarily determined by the alcohol used and the ratio of alcohol to theseparated quantity of water. Alcohols in which the OH groups interact bymeans of conjugated π electron systems, such as for examplehydroquinone, have a stronger tendency to form Si(R₂)—OR′—OSiR₂ groupsin the siloxane chain, than alcohols, such as for example2,2-bis(4-hydroxycyclohexyl)propane, in which there is no interactionbetween the OH groups.

In those compounds having a primary and a secondary OH group, the morereactive primary OH group reacts preferentially with the siloxane.

The process according to the invention may be terminated by neutralisingthe catalyst. Preferred neutralising agents for the neutralisation arethose which may be completely removed from the product once the reactionmixture has been worked up. NaHCO₃, soda and (NH₄)₂CO₃ are preferred inthe case of acidic catalysis, while (CH₃)₃SiCl is preferred in the caseof basic catalysis. The reaction mixture is preferably worked up byremoving solvent and remaining cyclic compounds as well as any remainingvolatile compounds of the type HOR′X by distillation under reducedpressure, and filtering out the neutralised equilibration catalyst andthe remaining solid compounds of the type HOR′X.

The present invention additionally provides the use of theorganofunctional siloxanes produced using the process according to theinvention for modifying organic polymers. In this case, theO—Si(R₂)—O—R′X groups formed are intended to react with the organicmonomers or oligomers, resulting in incorporation into the polymerbackbone.

The following non-limiting Examples are intended to illustrate theinvention in greater detail.

PRACTICAL EXAMPLES Example 1

740 g of octamethylcyclotetrasiloxane, 300 g of xylene and 73.3 g ofhydroquinone were initially introduced into an inertised flask equippedwith a thermometer, stirrer, water separator and reflux condenser. Afterpurging with nitrogen, 1000 ppm of 98% sulfuric acid and 500 ppm ofperfluoroalkylsulfonic acid were added. After heating to reflux, 6 ml ofwater were removed from the system within 30 minutes. The temperaturewas then rapidly reduced to 60° C. and stirring continued for two hoursat 60° C. Once the catalyst had been neutralised with ammoniumcarbonate, volatile constituents were removed from the reaction mixturefor 1 hour at 150° C. and a pressure of <1 mbar and the temperature wasreduced to room temperature. Free hydroquinone, excess neutralisingagent and the neutralisation products of the acids were then removedfrom the remaining residue by filtration through a Seitz vacuum filter,lined with a type K 300 filter, obtainable from the company Seitz,Germany. A clear to slightly turbid polysiloxane was obtained having aviscosity of 700 mPas at 23° C. and a composition, determined by ¹H and²⁹Si spectroscopy, of:

HO[C₆H₄—O—(—SiR₂O_({fraction (2/2)}))₂₃]₄₋₅C₆H₄OH.

Example 2

740 g of octamethylcyclotetrasiloxane, 300 g of xylene and 50 g ofisopropanolamine were initially introduced into an inertised flaskequipped with a thermometer, stirrer, water separator and refluxcondenser. After purging with nitrogen, 4000 ppm of potassium hydroxidewere added. After heating to reflux, 6 ml of water were removed from thesystem within 3 hours. The temperature was then reduced to 100° C., thecatalyst neutralised with trimethylchlorosilane and volatileconstituents were removed from the reaction mixture for 1 hour at 150°C. and a pressure of <1 mbar. After cooling to room temperature,potassium chloride was removed from the remaining residue by filtrationthrough a Seitz vacuum filter, lined with a type K 300 filter(obtainable from the company Seitz, Germany). A clear to slightly turbidpolysiloxane was obtained having a viscosity of 20 mPas at 23° C. and acomposition, determined by ¹H spectroscopy, of:

[H₂NCH₂CH(CH₃)O_(½)]₂[(CH₃)₂SiO_({fraction (2/2)})]₁₄.

Example 3

740 g of octamethylcyclotetrasiloxane, 300 g of xylene and 240 g of2,2-bis(4-hydroxycyclohexyl)propane were initially introduced into aninertised flask equipped with a thermometer, stirrer, water separatorand reflux condenser. After purging with nitrogen, 1000 ppm of potassiumhydroxide were added and, after heating to reflux, 18 ml of water wereremoved from the system within 2 hours. Once the catalyst had beenneutralised with trimethylchlorosilane, volatile constituents wereremoved from the reaction mixture for 1 hour at 150° C. and a pressureof <1 mbar. After cooling to room temperature, free2,2-bis(4-hydroxycyclohexyl)propane and potassium chloride were removedfrom the remaining residue by filtration through a Seitz vacuum filter,lined with a type K 300 filter, obtainable from the company Seitz,Germany. A clear to slightly turbid polysiloxane was obtained having aviscosity of 2000 mPas at 23° C. and a composition, determined by ¹H and²⁹Si spectroscopy, of:

HO[Z—O((CH₃)₂SiO_({fraction (2/2)}))₁₄]₁₃Z—OH

Example 4

740 g of octamethylcyclotetrasiloxane, 300 g of xylene and 78.8 g of2,5-hexanediol were initially introduced into an inertised flaskequipped with a thermometer, stirrer, water separator and refluxcondenser. After purging with nitrogen, 2000 ppm of potassium hydroxidewere added and, after heating to reflux, 6 ml of water were removed fromthe system within 2 hours. Once the catalyst had been neutralised withtrimethylchlorosilane, volatile constituents were removed from thereaction mixture for 1 hour at 150° C. and a pressure of <1 mbar. Aftercooling to room temperature, potassium chloride was removed from theremaining residue by filtration through a Seitz vacuum filter, linedwith a type K 300 filter, obtainable from the company Seitz, Germany. Aclear to slightly turbid polysiloxane was obtained having a viscosity of260 mPas at 23° C., an OH value of 19 mg of KOH/g and a composition,determined from ¹H and OH value, of:

HO[CH(CH₃)(CH₂)₂CH(CH₃)O[(CH₃)]₂SiO_({fraction (2/2)})]₅₇]_(1.3)CH(CH₃)CH₂CH₂CH(CH₃)OH.

Example 5

740 g of octamethylcyclotetrasiloxane, 300 g of xylene and 107 g of2,2-bis-hydroxymethyl-1-butenol diallyl ether were initially introducedinto an inertised flask equipped with a thermometer, stirrer, waterseparator and reflux condenser. After purging with nitrogen, 2000 ppm ofpotassium hydroxide were added and, after heating to reflux, 4.5 ml ofwater were removed from the system within 3 hours. Once the catalyst hadbeen neutralised with trimethylchlorosilane, volatile constituents wereremoved from the reaction mixture for 1 hour at 150° C. and a pressureof <1 mbar. After cooling to room temperature, potassium chloride wasremoved from the remaining residue by filtration through a Seitz vacuumfilter, lined with a type K 300 filter, obtainable from the companySeitz, Germany. A clear to slightly turbid polysiloxane was obtainedhaving a viscosity of 100 mPas at 23° C. and a composition, determinedby ¹H spectroscopy, of:

[(CH₂═CH—CH₂OCH₂)₂C(C₂H₅)CH₂O_(½)]₂[(CH₃)₂SiO_({fraction (2/2)})]₅₇.

Example 6

695 g of octamethylcyclotetrasiloxane, 300 g of xylene, 53.5 g of2,2-bis-hydroxymethyl-1-butenol diallyl ether and 66.5 g of atrimethylsiloxy end-stopped siloxane having 5 (CH₃)₂SiO units wereinitially introduced into an inertised flask equipped with athermometer, stirrer, water separator and reflux condenser. Afterpurging with nitrogen, 2000 ppm of potassium hydroxide were added and,after heating to reflux, 2.25 ml of water were removed from the systemwithin 3 hours. Once the catalyst had been neutralised withtrimethylchlorosilane, volatile constituents were removed from thereaction mixture for 1 hour at 150° C. and a pressure of <1 mbar. Aftercooling to room temperature, potassium chloride was then removed fromthe remaining residue by filtration through a Seitz vacuum filter, linedwith a type K 300 filter, obtainable from the company Seitz, Germany. Aclear to slightly turbid polysiloxane was obtained having a viscosity of100 mPas at 23° C. and a composition, determined by ¹H and ²⁹Si nuclearmagnetic resonance spectroscopy, of:

[(CH₂═CH—CH—O—CH₂)₂C(C₂H₅)O_(½)]₁[(CH₃)₂SiO]₅₇[O_(½)Si(CH₃)₃]₁.

What is claimed is:
 1. Process for the production of organofunctionalpolydiorganosiloxanes of the formula (I)[R₂(XR′O)SiO_(½)]_(a)[R₂SiO_({fraction (2/2)})]_(b)[R₃SiO_(½)]_(2-a)where 0<a≦2, b=0-500, and with the proviso that where b=0, a is 2 in thetotal, X═—OH, —COOH, —NR″₂, —CR″═CR″₂, R═C₁-C₁₈ alkyl, C₆-C₁₄ aryl andR′═C₂-C₁₈ alkylene, oxyalkylene, C₆-C₁₄ arylene and R″═H and/or C₁-C₁₈alkyl, wherein the [R₂SiO_({fraction (2/2)})] units are optionallyattached together via O—R′—O linkages, wherein at least one cyclicdialkylsiloxane is reacted with at least one compound of the typeHO—R′—X in the presence of at least one equilibration catalyst,optionally in the presence of linear trialkylsiloxy-terminatedsiloxanes, where alkyl=C₁-C₁₈ alkyl, and optionally in a hydrophobicsolvent at temperatures of between 80 and 220° C.
 2. Process accordingto claim 1, wherein the cyclic dialkylsiloxane used comprises compoundswhich have 4, 5 or 6 silicon atoms and bear methyl residues as the alkylresidues.
 3. Process according to claim 1 wherein the cyclicdialkylsiloxane used comprises a mixture of cyclic dialkylsiloxane andup to 50 wt. % of short-chain hydroxy-terminated dialkylpolysiloxanes.4. Process according to claim 1, wherein the equilibration catalyst usedcomprises perfluoroalkylsulfonic acids, individually or mixed withsulfuric acid, or alkali metal hydroxides.
 5. Process according to claim1, wherein the equilibration catalyst is used in quantities of 500 to5000 ppm, relative to the quantities of cyclic dialkylsiloxane and thecompound of the type HO—R′—X.
 6. Process according to claim 1, whereinthe hydrophobic solvent used comprises those which have a boiling pointof ≧100° C. at atmospheric pressure, form an azeotropic mixture withwater or both.
 7. Process according to claim 1, wherein xylene, toluene,chlorobenzene, or a combination thereof, is used as the solvent. 8.Process according to claim 1, wherein the cyclic dialkylsiloxane is usedin a ratio of 1 to 500 mol of dialkylsiloxy groups to 2 mol of thecompound of the type HO—R′—X.
 9. A method for modifying organic polymerswhich comprises reacting the organofunctional polydiorganosiloxanes ofclaim 1 with said polymers or with monomers or oligomers from which saidpolymers are formed.